Improve docs for postgresql with uuid primary keys [ci skip]

Introduced in 09ac1776ab.

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -340,10 +340,10 @@ module ActiveRecord
         #   end
         #
         # By default, this will use the +uuid_generate_v4()+ function from the
-        # +uuid-ossp+ extension, which MUST be enabled on your databse.  To enable
+        # +uuid-ossp+ extension, which MUST be enabled on your database. To enable
         # the +uuid-ossp+ extension, you can use the +enable_extension+ method in your
-        # migrations To use a UUID primary key without +uuid-ossp+ enabled, you can
-        # set the +:default+ option to nil:
+        # migrations. To use a UUID primary key without +uuid-ossp+ enabled, you can
+        # set the +:default+ option to +nil+:
         #
         #   create_table :stuffs, id: false do |t|
         #     t.primary_key :id, :uuid, default: nil
@@ -354,11 +354,10 @@ module ActiveRecord
         # You may also pass a different UUID generation function from +uuid-ossp+
         # or another library.
         #
-        # Note that setting the UUID primary key default value to +nil+
-        # will require you to assure that you always provide a UUID value
-        # before saving a record (as primary keys cannot be nil).  This might be
-        # done via the SecureRandom.uuid method and a +before_save+ callback,
-        # for instance.
+        # Note that setting the UUID primary key default value to +nil+ will
+        # require you to assure that you always provide a UUID value before saving
+        # a record (as primary keys cannot be +nil+). This might be done via the
+        # +SecureRandom.uuid+ method and a +before_save+ callback, for instance.
         def primary_key(name, type = :primary_key, options = {})
           return super unless type == :uuid
           options[:default] = options.fetch(:default, 'uuid_generate_v4()')

activerecord/test/cases/adapters/postgresql/uuid_test.rb

@@ -59,7 +59,6 @@ class PostgresqlUUIDTestNilDefault < ActiveRecord::TestCase
 
   def setup
     @connection = ActiveRecord::Base.connection
-
     @connection.reconnect!
 
     @connection.transaction do